Accident site scaring and damage to the main rotor blades indicate that the rotor blades struck a rock formation while the helicopter was manoeuvring, likely descending, at slow speed. These indicators also suggest that the initial impact was made as the blades were advancing on the left side of the aircraft. The initial impact forces to the main rotor destroyed the rotor system, making the helicopter uncontrollable. Because no indication was found of any malfunction or pre-existing mechanical defect, further analysis focusses on operational aspects of the accident flight. The ravine was off the track that joined the lake and the airport, and since there were no apparent tourist attractions in the ravine, it is likely that the pilot flew into the ravine because of low visibility. The pilot did not cross the ravine at its mouth, which would indicate that the visibility at the time was less than the distance that spans the mouth and was probably equal to or less than the distance that spans the ravine in the vicinity of the accident site. When flying up the ravine abeam the accident site, the distance from the pilot's seat to the site is about 75 feet; and, because the helicopter had gone this far up the ravine, it is likely that the flight visibility was 75 feet or less. In this reduced visibility, the pilot would probably have slowed the helicopter to a hover close to terrain and navigated with reference to ground features. When flying a path from the southwest side of the ravine to the northeast side and trying to fly down the ravine back into the valley, the rock formation that was struck, which blends into the background, could initially be disregarded as not obtrusive. This rock formation would be on the pilot's blind side, aft left, as he focussed on the next clump of trees below. It is possible that the pilot, flying this path, descended onto the aforementioned rock formation with little or no sense of how close it was. It is possible that the pilot was not acutely aware of how much more room was needed to clear obstacles on his left side, since he had limited experience flying the AS350BA. Generally, there was little direct supervision of the accident pilot's operational activities. He was used to running the operation on his own, as the chief pilot did not live near the company's main operation. Specifically, on the day of the occurrence, the chief pilot was not in Squamish, leaving the pilot to rely on his own judgment and abilities to assess the safety of operating in poor or changing weather conditions. There are inherent difficulties in enforcing flight visibility regulations for operators of small commercial aircraft. TC inspectors are not able to determine pilot practices adequately nor the amount or quality of supervision. Also, with current regulations, they have difficulty enforcing flight visibility regulations. Therefore, the accident pilot was operating with ineffective operational supervisory and regulatory defences with regard to poor weather operations.Analysis Accident site scaring and damage to the main rotor blades indicate that the rotor blades struck a rock formation while the helicopter was manoeuvring, likely descending, at slow speed. These indicators also suggest that the initial impact was made as the blades were advancing on the left side of the aircraft. The initial impact forces to the main rotor destroyed the rotor system, making the helicopter uncontrollable. Because no indication was found of any malfunction or pre-existing mechanical defect, further analysis focusses on operational aspects of the accident flight. The ravine was off the track that joined the lake and the airport, and since there were no apparent tourist attractions in the ravine, it is likely that the pilot flew into the ravine because of low visibility. The pilot did not cross the ravine at its mouth, which would indicate that the visibility at the time was less than the distance that spans the mouth and was probably equal to or less than the distance that spans the ravine in the vicinity of the accident site. When flying up the ravine abeam the accident site, the distance from the pilot's seat to the site is about 75 feet; and, because the helicopter had gone this far up the ravine, it is likely that the flight visibility was 75 feet or less. In this reduced visibility, the pilot would probably have slowed the helicopter to a hover close to terrain and navigated with reference to ground features. When flying a path from the southwest side of the ravine to the northeast side and trying to fly down the ravine back into the valley, the rock formation that was struck, which blends into the background, could initially be disregarded as not obtrusive. This rock formation would be on the pilot's blind side, aft left, as he focussed on the next clump of trees below. It is possible that the pilot, flying this path, descended onto the aforementioned rock formation with little or no sense of how close it was. It is possible that the pilot was not acutely aware of how much more room was needed to clear obstacles on his left side, since he had limited experience flying the AS350BA. Generally, there was little direct supervision of the accident pilot's operational activities. He was used to running the operation on his own, as the chief pilot did not live near the company's main operation. Specifically, on the day of the occurrence, the chief pilot was not in Squamish, leaving the pilot to rely on his own judgment and abilities to assess the safety of operating in poor or changing weather conditions. There are inherent difficulties in enforcing flight visibility regulations for operators of small commercial aircraft. TC inspectors are not able to determine pilot practices adequately nor the amount or quality of supervision. Also, with current regulations, they have difficulty enforcing flight visibility regulations. Therefore, the accident pilot was operating with ineffective operational supervisory and regulatory defences with regard to poor weather operations. At the time of the accident, the visibility at the accident site was concluded to have been about 75 feet. The helicopter was being flown in weather below the minimum visibility limits for aerial work (sightseeing) operations. While the helicopter was being manoeuvred close to terrain in poor visibility, the helicopter's main rotor struck a rock, making the helicopter uncontrollable. The pilot had limited experience in helicopter operations, and he was operating without effective operational supervision and regulatory defences.Findings as to Causes and Contributing Factors At the time of the accident, the visibility at the accident site was concluded to have been about 75 feet. The helicopter was being flown in weather below the minimum visibility limits for aerial work (sightseeing) operations. While the helicopter was being manoeuvred close to terrain in poor visibility, the helicopter's main rotor struck a rock, making the helicopter uncontrollable. The pilot had limited experience in helicopter operations, and he was operating without effective operational supervision and regulatory defences. The pilot seat position, relative to the rotor disc, is different in the accident helicopter than in the helicopter in which the pilot received his formative training. The emergency locator transmitter was destroyed by impact forces, and no emergency locator transmitter signal was received at any time. The ELT's location and construction are common for light helicopters.Findings as to Risk The pilot seat position, relative to the rotor disc, is different in the accident helicopter than in the helicopter in which the pilot received his formative training. The emergency locator transmitter was destroyed by impact forces, and no emergency locator transmitter signal was received at any time. The ELT's location and construction are common for light helicopters. The aircraft loading configuration, with respect to fuel, passengers, and cargo, was appropriate for the flight. No indication was found of any malfunction or pre-existing mechanical defect with the helicopter, its engine, or its systems.Other Findings The aircraft loading configuration, with respect to fuel, passengers, and cargo, was appropriate for the flight. No indication was found of any malfunction or pre-existing mechanical defect with the helicopter, its engine, or its systems. Safety Action from TSB occurrence report A95H0012 states, in part, The Department of Transport develop and implement a targeted national promotion campaign aimed at raising commercial operators' awareness of the inherent risks associated with flight operations in marginal VFR flight conditions. The Department of Transport develop and implement a targeted national promotion campaign aimed at raising commercial operators' awareness of the inherent risks associated with flight operations in marginal VFR flight conditions. In response, TC stated that it conducts Pilot Decision Making (PDM) courses, workshops, and briefings in all regions. A Notice of Proposed Amendment (NPA) for the CARs, issued 05 November 1999, changes the requirement for PDM training from one time to annually. Aviation Safety Information letter 950202 (TSB occurrence A95C0197), refers to ELT deficiencies, including the location of ELT installations on helicopters. The letter also refers to occurrence A95W0177: on 19 September 1995, following a collision in flight, Hughes 369D, C-GTZM and C-GXKF crashed and burned. The wreckage of the two helicopters was located about 70 miles east of Yellowknife, Northwest Territories. The ELTs in both helicopters were mounted in the front of the cabin and were destroyed. The tail booms of both helicopters survived the impact with relatively little damage. The TSB is of the opinion that ELTs would be better located in the tail sections of helicopters. The Board is not aware of any changes in ELT installation practices that would enhance the survivability of ELTs in helicopter accidents.Safety Action Safety Action from TSB occurrence report A95H0012 states, in part, The Department of Transport develop and implement a targeted national promotion campaign aimed at raising commercial operators' awareness of the inherent risks associated with flight operations in marginal VFR flight conditions. The Department of Transport develop and implement a targeted national promotion campaign aimed at raising commercial operators' awareness of the inherent risks associated with flight operations in marginal VFR flight conditions. In response, TC stated that it conducts Pilot Decision Making (PDM) courses, workshops, and briefings in all regions. A Notice of Proposed Amendment (NPA) for the CARs, issued 05 November 1999, changes the requirement for PDM training from one time to annually. Aviation Safety Information letter 950202 (TSB occurrence A95C0197), refers to ELT deficiencies, including the location of ELT installations on helicopters. The letter also refers to occurrence A95W0177: on 19 September 1995, following a collision in flight, Hughes 369D, C-GTZM and C-GXKF crashed and burned. The wreckage of the two helicopters was located about 70 miles east of Yellowknife, Northwest Territories. The ELTs in both helicopters were mounted in the front of the cabin and were destroyed. The tail booms of both helicopters survived the impact with relatively little damage. The TSB is of the opinion that ELTs would be better located in the tail sections of helicopters. The Board is not aware of any changes in ELT installation practices that would enhance the survivability of ELTs in helicopter accidents.